This invention relates to a storage device for supporting hollow shank tools, especially in a machine tool.
One form of tool holder used for mating a variety of tools to a common machine tool spindle, has a hollow shank that includes an outer locating surface of circular cross section (often tapered), adapted for seating in a complementary mating socket of the machine tool spindle.
A straight hollow shank toolholder is shown in European patent 310942A, of Hertel Werkzeuge AG, dated Aug. 10, 1987. This toolholder is shown within a machine spindle, where radially movable gripping elements comprise a plurality of balls, situated adjacent a ramp portion of an axially movable drawbar, inside the tool shank; the balls, in turn, force arcuate segments outwardly, to securely hold the tool.
A tapered hollow shank toolholder is exemplified by the "HSK toolholder". HSK is a special form, corresponding to a "DIN" (German engineering standard), for short, hollow, tapered tool shanks, wherein a tool shank is mounted to a spindle on both its conical surface, and the adjacent face formed on its integral toolchanger gripping flange. The taper is manufactured to very close tolerances, for accurate positioning at the spindle taper gage line. Unlike well-known ANSI (American National Standards Institute) standard solid toolholders, which are pulled into a spindle seat by way of a retention stud extending from the shank, an HSK tool shank has an internal relief, or retaining groove, so that, once inside a machine spindle, internal gripping fingers of the spindle assembly direct outward and rearward forces against the tool shank, to retain it securely with the spindle. An axial retention force of about 10,000 lbs is typically applied by a belleville spring stack, and overcome by a powered unit such as a hydraulic cylinder. This internal gripping arrangement is especially desirable for use in high speed applications, where centrifugal forces will work in the same direction as clamping forces applied to the tool shank. HSK tool shanks are manufactured in several forms, including both a keyless, frictionally driven style, and a positively driven style, having drive keyways at the small end of the taper.
Low-force analogues of spindle gripping arrangements have been proposed for retaining hollow shank tools within tool storage pockets; one example comprises a lightly loaded ball retention system, wherein balls are spring loaded against the tool retention groove. Such a tool storage pocket is shown in Japanese patent No. 8019929, dated Jan. 23, 1996, of Mori Machinery KK. In this case, a spring loaded conic member cams against several balls which are forced radially outward into the retention groove of a hollow tool shank; a separate device overcomes the spring force. Another example of a ball retention mechanism utilized in a tool storage device for supporting hollow shank tools is shown in U.S. Pat. No. 3,492,717, of Seidel et al, dated Feb. 3, 1970. At FIG. 2 of that patent, the tool shank is shown supported in a tool storage socket, and the end of each tool is provided with a bore having an inwardly-directed flange. A slidably mounted spool member has a double-cone groove which is spring-biased against a stop in the socket. The groove cams against a detent ball, and pushes it laterally behind the flange to hold the tool securely in the socket. A separate, movable arm contacts the spool member and pushes on it, to overcome the spring, so that the ball is free to move radially inwardly and release the tool.
In the prior art ball detent storage devices mentioned, an external actuating means must be employed to release the tool from its tool storage receptacle. In certain instances, the actuating means will take up an appreciable amount of space, typically along an axial direction, in order to accomplish the release of the balls.
The present invention obviates certain difficulties inherent in applying prior art ball detent devices, by utilizing a compact ring detent for holding tools within a tool storage module, which avoids the single point wear condition commonly associated with ball clamps.